G2p Analysis Minutes

Minutes of the weekly analysis meetings

Agenda

2/11/2015

Present: Chao, Jie, Min, Melissa
By Phone: Pengjia, Toby, Ryan, Ellie, Vince

Feature Presentations:

Toby
- Gave an update on dilution analysis. The dilution factor is define as one minus the ratio of background yield over
  total yield. The background yield includes contributions from nitrogen, helium and the foil endcap on the target cell.
  To extract the dilution factor he must tune the Bosted model (for helium and carbon) to match cross section data,
  radiate the simulation results and take ratios to obtain necessary scaling constants, and then apply these scaling
  constants to calculate the background yield. For tuning the Bosted model, he is currently using cross section data
  from the UVa quasi-elastic database. The kinematics do not match ours exactly, but this will work until g2p cross
  sections are available. He used a χ-squared minimization routine to determine the scaling factor for each kinematic.
  He also showed the resulting cross sections ratios, which are used to determine the scaling factors α, β and γ.
  Next he will apply the cross section ratios to yields from dilution runs to calculate the background yields and dilution
  factor for the 2.2 GeV, 5T transverse setting, after which he will move on to other settings. More details can be seen
  in his slides here.

2/4/2015

Present: Chao, JP, Jie, Min, Melissa
By Phone: Toby, Ryan, Pengjia, Karl

Feature Presentations:

Chao
- Gave a status update on optics analysis. For the 2.2 GeV, 5T settings (longitudinal and transverse) there was
  limited optics data taken. Instead, the 1.7 GeV optics matrix matrix was used for this setting, with a 0th order
  correction for the longitudinal setting, and a 1st order correction for the transverse setting. He showed the
  longitudinal setting as an example, applying the 1.7 GeV matrix and including the 0th order correction to center
  the sieve holes. JP commented that, if the offset is large, there may be higher order effects to consider. There
  are no optics runs for the 3.3 GeV setting, so he plans to use g2psim to determine the optics matrix. He is
  working on an optics technote, and a technote summarizing the last target field measurement. More details can
  be seen in his slides here.

Min
- Gave an update on her acceptance study. For this time, she improved the fitting at the virtual plane (for both
  x/y and , and θ/φ) and projected the results onto the focal plane. The corrections on the forward transport
  function were incorporated into g2psim. For the reverse transport function, the fit was done using all dp scan runs.
  The simulation does not match with the data at the edges; this is due to the boundary conditions in the simulation.
  Min will try expanding the boundary to see if it better matches the data. More details can be seen in her slides here.

Melissa
- Updated the data quality check for the 2.2 GeV, 2.5T setting to include RHRS runs. In general the problem
  settings on the RHRS are consistent with the LHRS. She also gave an update on the packing fraction analysis;
  there was a problem in the previous definition of the packing fraction. The updated method requires some input
  from cross section models. The resulting packing fraction is slightly larger than the result from the previous
  method. Next she will work on extracting packing fraction values for other settings. More details can be seen
  in her slides here.

Jie
- Calculated the energy loss using two methods; using his energy loss model (Monte Carlo, step by step), and
  using a radiated cross section model (from Stein). He used a fixed initial energy and fixed scattering angle for
  a carbon target, and didn't apply any acceptance cuts. He compared the dp spectra for the two methods and
  found that his energy loss model agrees well with the radiation model. Next he will work on a full simulation
  for a beam dependence study (once the acceptance is ready). More details can be seen here.

General Discussion:

Starting next week we will change the meeting start time to 9:30am.

1/28/2015

Present: Chao, JP, Jie, Melissa
By Phone: Vince, Ryan, Toby, Min, Pengjia, Ellie, Alexandre

Feature Presentations:

Ryan
- Gave an update on data quality checks for the 1.1 GeV setting. He found that the spread in yields ranges
  from 0.01% - 6.1%, with an average of ~2%. For this setting we also took runs on a short target cell (material
  14). For settings with a large spread, there was a correlation between beam drift and yield drift. Overall, this
  setting seems ok. Next he will move back to working on polarized radiative corrections. More details can be
  in his slides here, and a detailed summary
  of the data quality check can be seen here.

Pengjia
- Gave an update on data quality checks for the 1.7 GeV setting. For settings with a large spread in yields,
  he looked at the correlation with the calculated scattering angle. He found that in some cases the change in
  yield was proportional to the change in scattering angle, but for some settings it was inverse proportional.
  He also showed an example of a setting where the yield was drifting, but there was no change in the scattering
  angle. He tried applying raster cuts to see the effect on the yield, but first needs to find a way to calculate the
  charge while including the raster cut. There was some discussion how this could be done; it may be possible to
  use the Happex DAQ, as it is triggered by helicity. More details can be seen in his slides here.

General Discussion:

Toby will start replaying RHRS runs today, hopefully they will be done by the end of the week.

1/21/2015

Present: Jie, Min, Chao, JP, Kalyan, Melissa
By Phone: Pengjia, Vince, Ryan, Toby, Karl

Feature Presentations:

Melissa
- Gave a summary of data quality checks for the 2.2 GeV, 2.5T, transverse setting. There are several momentum
  settings with a significant spread (>2%) in the yields. In most cases, the spread in yields seems to be correlated
  with a change in beam position, which often corresponds to beam down time during the run period. Examples of
  problem settings can be seen in her slides here, and a summary of all settings is available here.

Chao
- Gave an update on the status of optics for the RHRS. For the longitudinal and transverse settings at 5T, only a
  few optics runs were taken, so the plan is to use the 1.7 GeV optics matrix for these settings. He also included a
  summary of the RMS value of each kinematic variable (δ, θ and φ) for each setting, and commented that
  the RMS value for y_tg is around 3-4mm, but this is a rough estimation as the fitting is not as good for this variable.
  Next he will test 2.5T transverse optics matrix on the 5T settings to see if it works. His slides are available here.
- The simulation package has been updated to cover the RHRS and include some upstream geometries. The most
  recent version of g2psim is available through github here: https://github.com/asymmetry/g2psim

Min
- Gave an update on her acceptance study. For this time, she combined all dp scan runs in order to do the
  corrections at the virtual plane, which was then projected onto the focal plane. The agreement at the virtual
  plane looks good, but there is still some disagreement at the focal plane. Next she will fit the reverse transport
  functions and compare target plane variables. More details are available in her slides here.

1/14/2015

Present: Chao, Jie, JP, Melissa
By Phone: Pengjia, Ryan, Toby, Ellie, Karl, Min, Vince, Alexandre

Feature Presentations:

Jie
- Gave an update on the dp simulation, specifically trying to understand why the simulation result for elastic dp was
  narrower than the data. Comparing the data (with just PID cuts) to the simulation result (using full acceptance, and
  a raster diameter of 2cm), the simulation is narrower than the data. However, if he applies acceptance cuts to the data
  and simulation, and uses a beam size of 4mm (which matches with the data), the results show a better match between
  data and simulation. He also tried dividing the beam spot into 5 different zones, and looked at the resulting dp
  distribution for each. He did see a shift in the central value of dp between zones, however this shift was not seen in the
  simulation. He also compared the shift in θ and φ for the 5 zones. JP commented that the θ distribution in
  the data is symmetric and centered around zero, while the simulation result is not. It is possible that this is due to the
  fact that Jie is using the old SNAKE model; he will get the updated version from Min and see if it makes a difference.
  More details can be see in his slides here.

Pengjia
- Posted his false asymmetry results to the ELOG.
- Working on data quality check for the 1.7 GeV, 2.5T setting. It looks like the spread in yields in some settings is
  strongly dependent on the scattering angle. JP suggested looking at beam position or other raw variables, since the
  scattering angle is a calculated value and depends on optics. It seems most settings with problems correspond to a
  break in time when the runs were taken, which may suggest a problem with the spectrometer. Pengjia will look into
  this next. More details can be seen in his slides here.

Toby
- Gave an update on his yield drift study for the 3.3 GeV setting. For this time, he looked at the target field (central
  NMR value) over the 2.34 GeV momentum setting, a period of about 6 hours. While there are some jumps in the signal,
  there isn't a consistent drift like is seen in the yields. However, there is a period where the signal jumps significantly; he
  will look into a possible cause for this. He also looked at the scaler BCM counts and trigger rates for these runs. There
  was no noticeable drift in the scaler rates, but the beam current was not stable during this time.. He also computed the
  "scaler yield" by dividing the total triggers by the BCM counts and saw a drift similar to what is seen in the normalized
  standard yield. Previous to these runs being taken, there was a flood in the hall resulting in a power outage. It's possible
  that the drifting is a result of systems not being stable while these runs were taken. More details can be seen in his
  slides here.

Ryan
- Working on a data quality check for the 1.1 GeV, 2.5T setting. In general the setting looks pretty good; the maximum
  spread is 10% and the minimum is 0.01%, with an average of ~2% spread. Fewer runs were taken in this setting, and the
  runs were taken consecutively, resulting in smaller spreads overall. In addition, there was data taken at this setting at
  3 different momentum settings, all looking at elastic, and all on the same material. Next he will try to determine the
  problem for the settings with a large spread (~10%). More details can be seen in his slides here.

1/7/2015

Present: Chao, Jie, JP, Min, Kalyan, Jixie, Melissa
By Phone: Yunxiu, Vince, Pengjia, Toby, Ryan, Ellie, Karl, Todd, Nilanga, Haiyan

Feature Presentations:

Each student gave a short update on their analysis projects since the last collaboration meeting on November 14th:

Melissa
- Method for packing fraction analysis is complete; the packing fraction values for each material still need to be
  extracted. This will probably take ~1 week, but the yield discrepancies need to be understood before it can be
  completed. She is also working on data quality checks for yields, specifically the 2.2 GeV, 2.5T setting. After these
  projects are complete she will work on the PbPt check using elastic asymmetries. More details can be seen in her
  slides here.

Toby
- Focusing on data quality checks of yields for production runs. He has completed the 2.2 GeV 5T settings, both
  longitudinal and transverse, and the 3.3 GeV setting. The 2.2 GeV 5T settings have few problems, but the 3.3 GeV
  has many momentum settings where the yields drift over time. He sees a similar drift in the left and right arm data.
  He is still trying to figure out the cause for the drift. In addition, he is working on tuning the Bosted model to helium
  and carbon dilution runs to simulate the background for dilution analysis, with a goal of finishing the dilution analysis
  by mid-march. More details can be seen in his slides here.
- Information on data quality checks can be found on the wiki here.

Jie
- Looked at the effect of changing the scattering angle on the cross section for carbon, nitrogen, helium and hydrogen.
  This may help explain the discrepancy we see in the yields, but is problem not the only cause. He is also working on
  finishing the dp simulation, which should be done soon, and will begin working with Min to learn more about the acceptance
  study. More details can be seen in his slides here.

Chao
- Gave an update on the status of optics analysis. He is finishing up the 2nd iteration of the optics calibration; the LHRS
  is complete and the RHRS has one setting to go (1.158 GeV). For the 2.2 GeV, 5T, transverse setting, there is no full
  dp scan, so the longitudinal data taken at that energy setting will be used. Once the 2nd iteration of the calibration is
  complete, he and Min will compile a technote on the optics study. He has also modified the geometry part of the g2psim
  package to make it more configurable. More details can be seen in his slides here.

Min
- Working on the acceptance study. In the focal plane, there seems to be good agreement between simulation and data.
  In the target plane, in the θ vs φ plot, there seems to be a shift in φ for all dp settings; it seems to be a linear
  correlation with dp. Next she will work on a correction for φ-target vs dp and compare target plane variables. To finish the
  good septum, straight through setting it will probably take 1-2 months, then an additional 1-2 months for the other 2 septum
  settings. More details can be see in her slides here.

Ryan
- He has completed a draft for a PRC paper on unpolarized He3 cross section data. He still needs to complete the He3 radiative
  correction analysis for saGDH, but is waiting on updated nitrogen cross sections for saGDH. He is also working on the carbon/
  nitrogen ratio for saGDH, but is waiting on updated analysis from Vince before continuing. He is also working on data quality
  checks for production runs for the 1.1 GeV setting, and is starting to look into polarized radiative corrections. More details can
  be seen in his slides here.

Pengjia
- Calculated the false asymmetry by comparing the asymmetry before and after applying detector cuts. He found the false
  asymmetry to be small; less than 200 ppm for all energy settings. He's also working on a data quality check for the 1.7 GeV
  data set. More details can be seen in his slides here.

General Discussion:

Yields stability/overall data quality check is the main issue at this time.
Progress of acceptance study looks good, but could become an analysis bottleneck.